The 2002 United States Senate election featured a series of fiercely contested elections that resulted in a victory for the Republican Party, which gained two seats and thus a narrow majority from the Democratic Party in the United States Senate. The Senate seats up for election, known as "class 2" Senate seats, were last up for regular election in 1996. The election was held on November 5, 2002, almost fourteen months after the September 11, 2001 attacks.

The Democrats had originally hoped to do well, as the party holding the presidency historically loses seats in midterm elections, and the Republicans had 20 seats up for election compared to 14 Democratic seats. In addition, four incumbent Republicans and no Democrats announced their retirement before the election. However, the Republicans were able to hold the four open seats, all of which were in the South. Ultimately, Republicans would pick up three seats and lose one, resulting in a net gain of two seats. Together with gains made in the House of Representatives, this election was one of the few mid-term elections in the last one hundred years in which the party in control of the White House gained Congressional seats (the others were 1902, 1934, and 1998).

This was the most recent Senate election cycle in which at least one incumbent senator from each party lost in the general election. This was also the second consecutive mid-term election held in a president's first term in which the Republican party both had a net gain of seats and regained control of the United States Senate from the Democratic Party. This was the only election cycle ever where the party of the incumbent President gained new control of a house of Congress.

Georgia: Sen. Max Cleland (D), a Vietnam War veteran and triple amputee, was defeated by Representative Saxby Chambliss in a tough campaign marked by attacks on Cleland's stance on a Department of Homeland Security. Even though Cleland was a combat veteran, Chambliss won the support of the VFW.

Missouri: Sen. Jean Carnahan (D) had been appointed to the Senate after her husband, Mel Carnahan, had narrowly won the 2000 election posthumously. How much Mel Carnahan's victory had been due to sympathy following his death and/or high disapproval of his opponent, John Ashcroft, was unclear, but his wife was unable to hold the seat, losing narrowly to former Congressman Jim Talent.

Minnesota: Sen. Paul Wellstone (D), in the middle of a tough fight against former St. Paul Mayor Norm Coleman, died in a plane crash less than two weeks before the election. Most observers expected that this would lead to a sympathy boost for his replacement, liberal stalwart and former Vice PresidentWalter Mondale, but the Democrats received negative press after Wellstone's funeral was marked by political speeches, and Coleman won a close race.

New Jersey: Democratic incumbent Robert Torricelli (D) was dogged by scandal, and eventually quit the race so that the party could replace him with a better candidate, retired Sen. Frank R. Lautenberg (D), who went on to win. Republicans challenged this late replacement of a weak candidate, but were not successful in the courts.

Louisiana: Republicans ran several candidates at once against incumbent Mary Landrieu (D), hoping to push her vote below 50% and force a runoff in December (according to Louisiana law). They did force a runoff, but Republican Suzanne Haik Terrell narrowly lost the runoff.

New Hampshire: Incumbent Senator Bob Smith (R) had previously quit and rejoined the Republican party in a dispute over his candidacy in the 2000 presidential election, and Republican leaders pushed the candidacy of Congressman John E. Sununu. He defeated Smith in the primary and went on to defeat Democrat Jeanne Shaheen, the retiring governor, in the general election. In this Senate race, local Republican officials violated election laws by trying to jam the phones of the Democrats' "Get Out The Vote" efforts; the officials went to prison in a case that reverberated into 2006 and may have been a factor when Sununu lost to Shaheen in their 2008 rematch.

Incumbent Paul Wellstone (DFL) ran for re-election, but died October 25, 2002.Dean Barkley (Reform) was appointed November 4, 2002 to finish the term, but Barkley did not run in the election.Republican gain